Drawing machines for metal products are known, such as solid or tubular bars, that comprise a drawing assembly provided with two counter-rotating tracks, opposite each other with respect to a drawing axis.
Each track includes a plurality of links constrained to each other in sequence, on each of which a drawing clamp is mounted that, during use, presses against at least one bar subjected to drawing.
In particular, each drawing clamp of one track cooperates with a corresponding drawing clamp present in the opposite track to clamp from opposite sides the bar subjected to drawing, in one of its segments that has already been drawn.
Each track is closed in a ring around a support plate and is made to rotate continuously by toothed wheels, generally two, one drive wheel and one driven, mounted on opposite ends of the same support plate.
It is known to interpose, between the support plate and the corresponding track, an intermediate chain of the type with rolls with the function of reducing the friction between the links of the track and the support plate, introducing a rolling type friction between the two components. In this way, intermediate chains act as bearings and allow to work at higher drawing speeds, thanks to the possibility of making the tracks rotate at higher rotation speeds.
Intermediate chains also have the function of discharging uniformly the thrusts that act on the individual links of the tracks.
It is known that intermediate chains are usually idle and receive motion from the tracks due to their contact with the links of said tracks.
Intermediate chains generally consist of links connected to each other with a desired play that allows to prevent the blockage of the movement of the intermediate chains.
Intermediate chains are known whose links each comprise an idle roll, two connection elements disposed symmetrically opposite each other at the two opposite longitudinal ends of the idle roll, and a join pin, passing axially inside the idle roll and inside through holes made in the connection elements.
The connection of consecutive links is achieved through connection of the respective connection elements, each of which is suitably configured to at least partly overlap two idle rolls.
In these known solutions, the transfer of the motion from the tracks to the intermediate chains occurs on the idle rolls, which therefore perform a drawing action on the links through the join pins connected to the connection elements.
One disadvantage of known intermediate chains is that the stresses to which the links of the chains are subjected are concentrated in the lateral housing and sliding seatings of the idle rolls provided in the connection elements: the lateral seatings are therefore subject to considerable wear. This entails frequent maintenance operations, and can also negatively affect the correct functioning of the intermediate chains in their entirety.
Another disadvantage of known intermediate chains is that, although flexible and light, they are subject to possible instability due to the idle rolls going off-axis if there is asymmetric wear of said housing and sliding seatings. This off-axis position can cause a deformation of the idle rolls and can also cause the corresponding intermediate chain to come out of its rotation seating, with the consequent possibility of damaging the intermediate chain itself, as well as the drawing assembly. This can be translated into a considerable economic damage due to the shutting down of the machine to restore the correct functioning of the drawing assemblies
One purpose of the present invention is to produce an intermediate chain that is able to reduce the wear of the housing and sliding seatings of the idle rolls, uniformly discharging onto the whole link the stresses deriving from the thrusts acting on the idle rolls.
Another purpose of the present invention is to produce an intermediate chain that has greater stability than that which can be obtained from known intermediate chains, and that is able to maintain said stability over time.
Another purpose of the present invention is to produce an intermediate chain that is simple to make and assemble, consisting of a limited number of components and that requires a reduced number of operations for its assembly.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.